A contemporary review of adult heart transplantation: 2012 to 2013

Transcatheter valvular interventions after heart transplantation: A systematic review

An increasing number of patients experience late valvular disease after heart transplantation (HTx). While mostly being primarily addressed through surgical interventions, transcatheter valve procedures to treat these conditions are rising, particularly for unsuitable surgical candidates. This review aims at analyzing the outcomes of transcatheter valvular procedures in this subset of patients. A systematic review was conducted including studies reporting on adult patients requiring any form of transcatheter valvular intervention after a previous HTx. Studies involving a surgical approach, heterotopic heart transplants, or concomitant procedures performed during the transplant itself were excluded. Twenty-five articles with a total of 33 patients met the inclusion criteria, 10 regarding the aortic valve (14 patients), 5 the mitral valve (6 patients), and 6 the tricuspid valve (13 patients). In two cases, the procedure was recommended to stabilize the valvular lesion before re-transplantation, as both were very young patients. Overall, the mean time from heart transplantation to reintervention was 14.7 ± 9.5 years. The mean follow-up was 15.5 ± 13.5 months, and only one patient died 22.3 months after the intervention. There is a growing emergence of transcatheter interventions for valvular disease after heart transplantation, especially in cases where surgery is deemed high-risk or prohibitive. A different strategy may also be considered in young patients to permit longer allograft life before later re-transplantation. Although encouraging outcomes have been documented, additional research is required to establish the most appropriate approach within this specific subset of patients.

Paradoxical outcome of heart transplantation associated with institutional case volume

BACKGROUND

Previous studies in heart transplantation have shown an association between institutional case volume and outcomes. We aim to determine the case volume associated with optimal 1-year survival after transplantation.

METHODS AND RESULTS

The United Network for Organ Sharing (UNOS) national database was analyzed for adult patients who underwent orthotopic heart transplantation between January 2013 and December 2017. A total of 11,196 cases at 128 transplant centers were included. Risk-adjusted restricted cubic splines revealed a non-linear association between institutional case volume and 1-year post-transplant survival. In the risk-adjusted, random-effect Cox model with segmented linear splines, higher heart transplant volume up to 24 cases per year was associated with better 1-year survival (HR = .978 every additional case, 95% CI .963-.993), and optimal survival was maintained between 24 and 38 cases per year. However, further increase in volume above 38 transplants per year was associated with mildly decreased 1-year survival (HR = 1.007 every additional case, 95% CI 1.002-1.013).

CONCLUSIONS

The relationship between institutional case volume and heart transplant 1-year survival is non-linear, with optimal survival observed at institutional case volume of 24-38 cases per year.

Analytical Validation of HEARTBiT: A Blood-Based Multiplex Gene Expression Profiling Assay for Exclusionary Diagnosis of Acute Cellular Rejection in Heart Transplant Patients

BACKGROUND

HEARTBiT is a whole blood-based gene profiling assay using the nucleic acid counting NanoString technology for the exclusionary diagnosis of acute cellular rejection in heart transplant patients. The HEARTBiT score measures the risk of acute cellular rejection in the first year following heart transplant, distinguishing patients with stable grafts from those at risk for acute cellular rejection. Here, we provide the analytical performance characteristics of the HEARTBiT assay and the results on pilot clinical validation.

METHODS

We used purified RNA collected from PAXgene blood samples to evaluate the characteristics of a 12-gene panel HEARTBiT assay, for its linearity range, quantitative bias, precision, and reproducibility. These parameters were estimated either from serial dilutions of individual samples or from repeated runs on pooled samples.

RESULTS

We found that all 12 genes showed linear behavior within the recommended assay input range of 125 ng to 500 ng of purified RNA, with most genes showing 3% or lower quantitative bias and around 5% coefficient of variation. Total variation resulting from unique operators, reagent lots, and runs was less than 0.02 units standard deviation (SD). The performance of the analytically validated assay (AUC = 0.75) was equivalent to what we observed in the signature development dataset.

CONCLUSION

The analytical performance of the assay within the specification input range demonstrated reliable quantification of the HEARTBiT score within 0.02 SD units, measured on a 0 to 1 unit scale. This assay may therefore be of high utility in clinical validation of HEARTBiT in future biomarker observational trials.

Endocrine disorders after heart transplantation: national cohort study

BACKGROUND

Endocrine disorders in patients after heart transplantation (HT) remain understudied. We aimed to assess endocrine profiles and management of HT recipients in the early post- transplant period.

METHODS

We conducted a retrospective cohort study on 123 consecutive HT recipients in the Advanced Heart Failure and Transplantation Programme between 2009 and 2018. All recipients had per-protocol endocrine follow-up within the first postoperative year. The median time to first post-transplant endocrine follow-up was 3 months (IQR 2-4). We assessed the incidence of vitamin D deficiency, bone mineral density, history of low energy fractures, hypogonadism in male recipients, posttransplant diabetes mellitus, and thyroid and parathyroid function.

RESULTS

We enrolled 22 women and 101 men of median age 57 years (IQR 50-63). Post-transplant diabetes mellitus developed in 14 patients (11.4%). 18 of 25 patients (14.6%) with preexisting type 2 diabetes mellitus required intensification of antidiabetic therapy. 38 male patients (40.4%) had hypogonadism. 5 patients (4.6%) were hypothyroid and 10 (9.3%) latent hyperthyroid. Secondary hyperparathyroidism was present in 19 (17.3%), 25-hydroxyvitamin D deficiency in 64 (54.7%) of patients. Osteoporosis was present in 26 (21.1%), osteopenia in 59 (48.0%) patients. 47 vertebral fractures, 3 hip and 1 humerus fractures occurred in 21 patients. Most of the patients had coincidence of two or three disorders, while less than 5% did not have any endocrine irregularities. All patients received calcium and vitamin D supplements. Forty-six patients (37.4%) were treated with zoledronic acid, 12 (9.8%) with oral bisphosphonates. Two patients were treated with teriparatide.

CONCLUSIONS

The prevalence of multiple endocrine disorders early after heart transplantation is high. Assessment and management of increased fracture risk and all other potentially affected endocrine axes should be considered as a standard of care in this early period.

Relationship Between Change in Heart Transplant Volume and Outcomes: A National Analysis

INTRODUCTION

Although volume-outcome relationships in transplantation have been well-defined, the effects of large changes in center volume are less well understood. The purpose of the current study was to examine the impact of changes in center volume on outcomes after heart transplantation.

METHODS

Retrospective analysis was performed of adult patients undergoing heart transplant between 2000 and 2017 identified in the United Network for Organ Sharing database. Exclusions included annual volume <10. Patients were grouped according to percentage change in center volume from the previous year. Multivariable Cox regression models were adjusted for the significant preoperative variance identified on univariate analyses.

RESULTS

Of the 29,851 transplants during the study period, 64% were at centers with stable volume (±25% annual change), whereas 10% were performed at contracting (-25% change or more) and 26% were performed at growing (+25% change or more) centers. Average volume was lower with contracting centers compared with stable or growing programs (21 vs 36, P< .001). Thirty-day mortality was greater in decreasing centers (6% vs 4%, P < .001), with more acute rejection treatments at 1y (27% vs 24% P < .001). The adjusted risk of mortality among contracting centers was 1.25 ([1.07-1.46], P= .004), whereas growing centers had unaffected risk (0.90 [0.79-1.02], P= .103). Causes of death were similar between groups.

CONCLUSIONS

Rapid growth of transplant center volume has occurred at select centers in the United States without decrement in programmatic outcomes. Decreasing center volume has been associated with poorer outcomes, although the causative nature of this relationship requires further investigation.

Risk Factors Associated With Peripheral Neuropathy in Heart Failure Patients Candidates for Transplantation

INTRODUCTION

Peripheral neuropathy can affect patients with heart failure, though its prevalence is unknown. After heart transplantation, it can influence the postoperative course and quality of life, but screening for neuromuscular disease is not routinely performed.

OBJECTIVE

The aim of this study was to identify the factors associated with neuropathy in a population of patients with heart failure who are candidates for heart transplantation.

STUDY DESIGN

Data regarding patients' clinical history, including recent hospitalizations, were collected. All patients underwent a complete neurological examination and a neurophysiological protocol including nerve conduction studies and concentric needle electromyography.

RESULTS

Thirty-two patients were included in the study, and neuropathy was diagnosed in 10 (31.3%). Neuropathy was associated with the number of admissions ( P = .023; odds ratio [OR]: 1.96) and the total number of days of hospitalization in the year prior to inclusion in the study ( P = .010; OR: 1.03). The majority of hospitalizations occurred in the step-down unit (85%), with acute heart failure the leading cause of admission (42%).

CONCLUSIONS

This study shows that neuropathy is frequent in patients with advanced heart failure and that hospitalization for cardiac care, also in the absence of intensive care, is a marker of high risk of neurologic damage. These data can help physicians in selecting and managing candidates for transplantation and can guide decisions on the best immunosuppressive regimen or rehabilitation strategy.

Primary graft dysfunction in heart transplantation

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) is common early postheart transplantation; however, use of standardized definitions remains inconsistent. This review focuses on understanding the incidence, classification, risk factors, and management of PGD.

RECENT FINDINGS

The incidence and mortality of PGD in heart transplant varies considerably in the published literature ranging from 1.0% to 31% and 3% to 75%, respectively. There is also considerable variation in management strategies with current data favoring early intervention.

SUMMARY

PGD in heart transplantation remains a challenging problem associated with significant mortality and morbidity. There is need for a consistent and accessible definition to better define associated risk factors and optimize management strategies.

The In-Hospital Cost of Ventricular Assist Device Therapy: Implications for Patient Selection

Ventricular assist device (VAD) therapy is increasingly utilized to support patients in end-stage heart failure. However, VAD programs are resource intensive and demand active monitoring to ensure long-term sustainability. The purpose of this study was to analyze total cost trends of the VAD program at our academic medical center. Retrospective analysis of University of California - Los Angeles's VAD program between 2013 and 2014 was performed. Total in-hospital costs from the date of VAD surgery admission were queried and normalized to a z score. Multivariable linear regression analysis with step-wise elimination was used to model total costs. Overall, 42 patients received a VAD during the study period, with 19 (45%) receiving biventricular support. On univariate analysis, high body mass index, biventricular support, time between VAD implantation and discharge, and total length of hospital stay were correlated with higher costs (all p < 0.02). On multivariable analysis, time between VAD implantation and discharge and biventricular support remained significantly related to total costs (overall R = 0.831, p < 0.001). The time between VAD implantation and discharge and the use of biventricular support were the most predictive factors of total cost in our VAD population. Reducing hospital stay post-VAD implantation is important in minimizing the cost of VAD care.

Effects of angiotensin-converting-enzyme inhibitor therapy on the regulation of the plasma and cardiac tissue renin-angiotensin system in heart transplant patients

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors (ACEis) are beneficial in patients with heart failure, yet their role after heart transplantation (HTx) remains ambiguous. Particularly, the effects of ACEis on plasma and cardiac metabolites of the "classical" and "alternative" renin-angiotensin system (RAS) in HTx patients are unknown.

METHODS

This cross-sectional study used a novel mass spectrometry-based approach to analyze plasma and tissue RAS regulation in homogenates of heart biopsy specimens from 10 stable HTx patients without RAS blockade and in 15 patients with ACEi therapy. Angiotensin (Ang) levels in plasma and Ang formation rates in biopsy tissue homogenates were measured.

RESULTS

Plasma Ang II formation is exclusively ACE dependent, whereas cardiac Ang II formation is primarily chymase dependent in HTx patients. ACEi therapy substantially increased plasma Ang-(1-7), the key effector of the alternative RAS, leaving plasma Ang II largely intact. Importantly, neprilysin and prolyl-carboxypeptidase but not angiotensin converting enzyme 2 are essential for cardiac tissue Ang-(1-7) formation.

CONCLUSION

ACE is the key enzyme for the generation of plasma Ang II, whereas chymase is responsible for cardiac tissue production of Ang II. Furthermore, our findings reveal that neprilysin and prolyl-carboxypeptidase are the essential cardiac enzymes for the alternative RAS after HTx. These novel insights into the versatile regulation of the RAS in HTx patients might affect future therapeutic avenues, such as chymase and neprilysin inhibition, beyond classical Ang II blockade.

Heart failure therapies: new strategies for old treatments and new treatments for old strategies

Heart failure, whether acute or chronic, remains a major health care crisis affecting almost 6 million Americans and over 23 million people worldwide. Roughly half of those affected will die within 5 years, and the annual cost exceeds $30 billion in the US alone. Although medical therapy has made some modest inroads in partially stemming the heart failure tsunami, there remains a significant population for whom medication is unsuccessful or has ceased being effective; such patients can benefit from heart transplantation or mechanical circulatory support. Indeed, in the past quarter century (and as covered in Cardiovascular Pathology over those years), significant improvements in pathologic understanding and in engineering design have materially enhanced the toolkit of options for such refractory patients. Mechanical devices, whether total artificial hearts or ventricular assist devices, have been reengineered to reduce complications and basic wear and tear. Transplant survival has also been extended through a better comprehension of and improved therapies for transplant vasculopathy and antibody-mediated rejection. Here we review the ideas and treatments from the last 25 years and highlight some of the new directions in nonpharmacologic heart failure therapy.

Twenty-Year Experience of Heart Transplantation: Early and Long-Term Results

Background

We evaluated early and long-term results after heart transplantation (HTPL).

Methods

One hundred five consecutive patients (male:female=80:25) who underwent HTPL between 1994 and 2013 were enrolled. Based on the changes in immunosuppressive regimen, the study patients were divided into two groups. Early and long-term clinical outcomes were evaluated and compared between the patients who underwent HTPL before (group E, n=41) and after July 2009 (group L, n=64). The group L patients were older (p<0.001), had higher incidence of hypertension (p=0.001) and chronic kidney disease (p<0.001), and more frequently needed preoperative mechanical ventilation (p=0.027) and mechanical circulatory support (p=0.014) than the group E patients.

Results

Overall operative mortality was 3.8%, and postoperative morbidities included acute kidney injury (n=31), respiratory complications (n=16), reoperation for bleeding (n=15) and wound complications (n=10). There were no significant differences in early results except acute kidney injury between group E and group L patients. Overall survival rates at 1, 5, and 10 years were 83.8%, 67.7%, and 54.9%, respectively, with no significant difference between the two patient groups. Rejection-free rates at 1 and 5 years were 63.0% and 59.7%, respectively; rates were significantly higher in group L than in group E (p<0.001).

Conclusion

Despite increased preoperative comorbidities, group L patients showed similar early and long-term outcomes and significantly higher rejection-free rates when compared with group E patients.

Variability in Physical Activity Assessed with Accelerometer Is an Independent Predictor of Mortality in CHF Patients

Aims

Patients with heart failure often display a distinct pattern of walking characterized by short step-length and frequent short pauses. In the current study we sought to explore if qualitative aspects of movement have any additive value to established factors to predict all-cause mortality in patients with advanced heart failure.

Methods and results

60 patients with advanced heart failure (NYHA III, peak VO2 <20 ml/kg and LVEF <35%) underwent symptom-limited CPX, echocardiography and routine chemistry. Physical activity was assessed using an accelerometer worn attached to the waist during waking hours for 7 consecutive days. The heart-failure survival score (HFSS) was calculated for each patient. All accelerometer-derived variables were analyzed with regard to all-cause mortality and added to a baseline model utilizing HFSS scores. HFSS score was significantly associated with the incidence of death (P<0.001; c-index 0.71; CI, 0.67–0.73). The addition of peak skewness to the HFSS model significantly improved the predictive ability with an increase in c-index to 0.74 (CI, 0.69–0.78), likelihood ratio P<0.02, establishing skewness as a predictor of increased event rates when accounting for baseline risk.

Conclusion

The feature skewness, a measure of asymmetry in the intensity level of periods of high physical activity, was identified to be predictive of all-cause mortality independent of the established prognostic model–HFSS and peak VO2. The findings from the present study emphasize the use of accelerometer analysis in clinical practice to make more accurate prognoses in addition to extract features of physical activity relevant to functional classification.

New Developments in HLA-G in Cardiac Transplantation

Human Leukocyte Antigen-G (HLA-G) is a non-classical class 1b protein, whose gene is located on chromosome 6 (6p21.31). HLA-G inhibits the immune cells' cytotoxic activity by interacting with specific receptors on their membranes. Since it is a naturally occurring immune modulator, HLA-G has been investigated in transplantation. Indeed, a number of investigations reveal that HLA-G expression is influenced by genetic polymorphisms and in turn, those polymorphisms are associated with detrimental or beneficial outcomes in various pathological situations. The present review introduces the HLA-G molecule, the gene and its polymorphisms. It focuses on the expression of HLA-G and the role of polymorphisms primarily in heart transplant outcomes, secondarily in other transplant organs, as well as the role of the allograft and effect of medical therapy. We discuss the limitations in HLA-G transplant investigations and future directions. The immune inhibiting activity of HLA-G has a great deal of potential for its utilization in enhancing diagnostic, preventive and therapeutic strategies against rejection in the setting of transplantation.

Pediatric heart transplantation

Pediatric heart transplantation (pHTx) represents a small (14%) but very important and particular part in the field of cardiac transplantation. This treatment has lifelong impact on children. To achieve the best short and especially long-term survival with adequate quality of life, which is of crucial importance for this young patient population, one has to realize and understand the differences with adult HTx. Indication for transplantation, waitlist management including ABO incompatible (ABOi) transplantation and immunosuppression differ. Although young transplant recipients are ultimately likely to be considered for re-transplantation. One has to distinguish between myopathy and complex congenital heart disease (CHD). The differences in anatomy and physiology make the surgical procedure much more complex and create unique challenges. These recipients need a well-organized and educated team with pediatric cardiologists and intensivists, including a high skilled surgeon, which is dedicated to pHTx. Therefore, these types of transplants are best concentrated in specialized centers to achieve promising outcome.